1. Field of the Invention
The present invention relates to an armature for a dynamo-electric machine in which side portions of adjacent coil portions, etc., share a slot.
2. Description of the Related Art
FIG. 11 is a side elevation of an armature 1 for a conventional motor. The armature 1 is disposed so as to be freely rotatable within a stator (not shown) having four poles. The armature 1 comprises: a motor shaft 2; a core 3 secured to the motor shaft 2 having slots 4 extending in the axial direction; a coil 6 composed of wires 5 coated with enamel wound around the core 3; and a commutator 8 secured to the motor shaft 2 at one end of the core 3.
The commutator 8 has twenty-one segments 11; insulating segments 10 electrically insulating the segments 11 from each other; and hooks 12 disposed so as to protrude from each of the segments 11 which are electrically connected to the wires 5.
FIG. 12 is a front elevation of the core 3. Twenty-one slots 4 are formed in the core 3 spaced equidistantly in the circumferential direction and teeth 9 are disposed between the slots 4. The coil 6 is composed of wires 5 wound onto the core by so-called “lap winding”.
FIGS. 13 to 15 are diagrams explaining the winding of the wires 5 onto the core 3 by the lap winding method.
FIG. 13 is a diagram showing the wires 5 being simultaneously supplied from the nozzles of a winding device (not shown) which winds the wires 5 onto the core 3, simultaneously forming a first coil portion A 30, a first coil portion B 31, and a first coil portion C 32, respectively. The first coil portion A 30 is formed by winding a wire 5 supplied from a first nozzle, for example, ten or so turns around tooth No. 2 of the teeth 9 and tooth No. 6 of the teeth 9 which are separated by four slots 4. The first coil portion B 31 is formed by winding a wire 5 supplied from a second nozzle, for example, ten or so turns around tooth No. 9 of the teeth 9 and tooth No. 13 of the teeth 9 which are separated by four slots 4. The first coil portion C 32 is formed by winding a wire 5 supplied from a third nozzle, for example, ten or so turns around tooth No. 16 of the teeth 9 and tooth No. 20 of the teeth 9 which are separated by four slots 4.
FIG. 14 is a diagram showing wires 5 continuing to be supplied from the nozzles of the winding device (not shown) after engaging the hooks 12, additionally forming a second coil portion A 36, a second coil portion B 37, and a second coil portion C 38, respectively.
FIG. 15 is a diagram showing the completed winding of the wires 5 between the teeth 9 of the core 3. A third coil portion A 42, a fourth coil portion A 45, a fifth coil portion A 48, a sixth coil portion A 51, and a seventh coil portion A 54 are additionally and continuously formed by the wire 5 supplied from the first nozzle. A third coil portion B 43, a fourth coil portion B 46, a fifth coil portion B 49, a sixth coil portion B 52, and a seventh coil portion B 55 are additionally and continuously formed by the wire 5 supplied from the second nozzle.
In the above motor, the armature 1 is rotated about the motor shaft 2 by electromagnetic action by supplying an electric current to the coil 6 from outside by means of brushes (not shown) which contact the segments 11. The segments 11 contacted by the brushes are switched in succession, switching the direction of the current supplied to the coil 6, so that whatever rotational position the armature 1 is in, the rotating force on the armature 1 is in a specific direction.
In the conventional (but not prior art) armature 1 described above, there are twenty-one slots 4 in total and three nozzles, the total number of slots 4 being evenly divisible by the number of nozzles, and the wires 5 are wound uniformly in each of the coil portions, making the impedance substantially the same in adjacent coils portions.
However, if, for example, the number of slots is increased from twenty-one to twenty-two in order to increase torque, and four nozzles are used to wind the wires onto such a core, as shown in FIG. 17, adjacent coil portions must share a slot along one side.
FIG. 17 is a diagram showing wires being simultaneously supplied to the core from four nozzles of a winding device (not shown) having two rotational angles, 98.2 degrees and 81.8 degrees, as shown in FIG. 16, simultaneously forming a first coil portion A 108, a first coil portion B 109, a first coil portion C 110, and a first coil portion D 111, respectively.
The first coil portion A 108 in FIG. 17 is formed by winding a wire supplied from a first nozzle, for example, ten or so turns around tooth No. 4 of the teeth 107 and tooth No. 22 of the teeth 107 which are separated by four slots 102. The first coil portion B 109 is formed by winding a wire supplied from a second nozzle, for example, ten or so turns around tooth No. 5 of the teeth 107 and tooth No. 9 of the teeth 107 which are separated by four slots 102. The first coil portion C 110 is formed by winding a wire supplied from a third nozzle, for example, ten or so turns around tooth No. 11 of the teeth 107 and tooth No. 15 of the teeth 107 which are separated by four slots 102. The first coil portion D 111 is formed by winding a wire supplied from a fourth nozzle, for example, ten or so turns around tooth No. 16 of the teeth 107 and tooth No. 20 of the teeth 107 which are separated by four slots 102.
In this case, the slot 102 between tooth No. 4 of the teeth 107 and tooth No. 5 of the teeth 107 is shared by a side portion of the first coil portion A 108 and a side portion of the first coil portion B 109, and the slot 102 between tooth No. 15 of the teeth 107 and tooth No. 16 of the teeth 107 is shared by a side portion of the first coil portion C 110 and a side portion of the first coil portion D 111.
For that reason, differences in impedance arise between the coil portions 108 to 111 in the slots 102 shared by the coil portions 108 to 111 because the wires are wound under conditions in which the coil portions 108 to 111 interfere with each other, leading to the following problems:
Differences in induced voltage arise in the coil portions 108 to 111 and unbalanced currents flow through the brushes, and as a result, the rectifying action of the brushes deteriorates, the temperature in the brushes and the commutator increases together with the increase in sparks generated by the brushes, the life of the brushes and the commutator is reduced, torque ripples increase, and the operating noise of the motor increases markedly due to the combined effects of the above.